This invention relates to thrombin inhibitors which are useful anticoagulants in mammals. In particular it relates to ortho-hydroxybenzamidine derivatives having high anticoagulant activity,. Thus, this invention relates to new inhibitors of thrombin, pharmaceutical compositions containing the compounds as active ingredients, and the use of the compounds as anticoagulants for prophylaxis and treatment of thromboembolic disorders such as venous thrombosis, pulmonary embolism, arterial thrombosis, in particular myocardial ischemia, myocardial infarction and cerebral thrombosis, general hypercoagulable states and local hypercoagulable states, such as following angioplasty and coronary bypass operations, and generalized tissue injury as it relates to the inflammatory process. In addition, the agents are useful as anticoagulants in in vitro applications.
The process of blood coagulation, thrombosis, is triggered by a complex proteolytic cascade leading to the formation of thrombin. Thrombin proteolytically removes activation peptides from the Axcex1-chains and the Bxcex2-chains of fibrinogen, which is soluble in blood plasma, initiating insoluble fibrin formation.
Anticoagulation is currently achieved by the administration of heparins and coumarins. Parenteral pharmacological control of coagulation and thrombosis is based on inhibition of thrombin through the use of heparins. Heparins act indirectly on thrombin by accelerating the inhibitory effect of endogenous antithrombin III (the main physiological inhibitor of thrombin). Because antithrombin III levels vary in plasma and because surface-bound thrombin seems resistant to this indirect mechanism, heparins can be an ineffective treatment. Because coagulation assays are believed to be associated with efficacy and with safety, heparin levels must be monitored with coagulation assays (particularly the activated partial thromboplastin time (APTT) assay). Coumarins impede the generation of thrombin by blocking the posttranslational gamma-carboxylation in the synthesis of prothrombin and other proteins of this type. Because of their mechanism of action, the effect of coumarins can only develop slowly, 6-24 hours after administration. Further, they are not selective anticoagulants. Coumarins also require monitoring with coagulation assays (particularly the prothrombin time (PT) assay).
Recently, interest has grown in small synthetic molecules which demonstrate potent direct inhibition of thrombin. See, for example Robert M. Scarborough, Annual Reports in Medicinal Chemistry, (1995), 30, 71-80, where inhibitors which lack a polarizable functionality to interact with the active site Ser-195 hydroxy group of thrombin are termed active site inhibitors. Active site inhibitors in which the C-terminal moiety comprises an unsubstituted or certain substituted amidinophenyl (benzamidine) moiety are exemplified in EP 623596, WO 94/29336, WO 95/23609 and WO 95/35309. The amidinophenyl moiety is strongly basic, a property which militates against good oral bioavailability. See, for example R. J. Misra, et al., Bioorganic and Medicinal Chemistry Letters, (1994), 4, 2165-2170, where less basic argatroban analogs were shown to retain useful thrombin inhibitory potency while exhibiting better distribution properties as shown by enhanced Caco-2 cell permeability. As discussed below, the compounds disclosed herein retain useful thrombin inhibitory potency while exhibiting improved distribution coefficients as a result of their particularly substituted amidinophenyl moieties. Subsequent to the priority date for the instant application, there were published international patent applications WO 96/24609 and WO 96/25426 disclosing certain substituted amidinophenyl compounds, including D-cyclohexylglycyl-N-[[4-(aminoimino-methyl)-3-hydroxyphenyl]methyl-L-prolinamide dihydrochloride at Example 53 of WO 96/25426.
Although the heparins and coumarins are effective anticoagulants, no generally accepted commercial drug has yet emerged from the small synthetic molecules; and despite the continuing promise for this class of compounds, there still exists a need for anticoagulants which act selectively on thrombin, and which, independent of antithrombin III, exert inhibitory action shortly after administration, preferably by an oral route, and do not interfere with lysis of blood clots, as required to maintain hemostasis.
The present invention is directed to the discovery that the compounds of the present invention, as defined below, are potent thrombin inhibitors that may have high bioavailability following oral administration.
According to the invention there is provided a compound having the Formula I
Xxe2x80x94C(O)xe2x80x94Yxe2x80x94Gxe2x80x94R xe2x80x83xe2x80x83I 
wherein
Xxe2x80x94C(O)xe2x80x94 is D-prolinyl, D-homoprolinyl, Rmxe2x80x94(CH2)gxe2x80x94NHxe2x80x94CH2xe2x80x94C(O)xe2x80x94, 
in which
Rd is carboxy or methylsulfonyl;
Re is NHRc, NHCORc or NHCOORc; in which
Rc is (C1-C6)alkyl, (C3-C8)cycloalkyl or a (C3-C8)cycloalkyl-(C1-C6)alkyl radical of 4-10 carbons;
T is (C3-C8)cycloalkyl, (C1-C8)alkyl, 
a is 0, 1 or 2; and
Q is xe2x80x94OH, (C1-C4)alkoxy, or xe2x80x94NHxe2x80x94A;
A is hydrogen, (C1-C4)alkyl, Rxe2x80x3SO2xe2x80x94, Rxe2x80x3OC(O)xe2x80x94, Rxe2x80x3C(O)xe2x80x94, RnC(O)xe2x80x94 or xe2x80x94(CH2)gxe2x80x94Rm;
g is 1, 2, or 3;
B is hydrogen or (C1-C4)alkyl;
Rxe2x80x2 is hydrogen or (C1-C4)alkyl;
Rxe2x80x3 is (C1-C4)alkyl, (C1-C4)fluoroalkyl bearing one to five fluoros, xe2x80x94(CH2)dxe2x80x94Rm, or unsubstituted or substituted aryl, where aryl is phenyl, naphthyl, a 5- or 6-membered unsubstituted or substituted aromatic heterocyclic ring, having one or two heteroatoms which are the same or different and which are selected from sulfur, oxygen and nitrogen, or a 9- or 10-membered unsubstituted or substituted fused bicyclic aromatic heterocyclic group having one or two heteroatoms which are the same or different and which are selected from sulfur, oxygen and nitrogen;
Rm is xe2x80x94COORb, xe2x80x94SO2(C1-C4 alkyl), xe2x80x94SO3H, xe2x80x94P(O) (ORb)2 or tetrazol-5-yl;
Rn is xe2x80x94COORb or tetrazol-5-yl;
each Rb is independently hydrogen or (C1-C4)alkyl;
d is 1, 2, or 3;
n is 0, 1, or 2;
n is 0, 1, or 2; and
Z is hydrogen, (C1-C4)alkyl, (C1-C4)alkoxy, hydroxy, halo or (C1-C4)alkylsulfonylamino;
xe2x80x94Yxe2x80x94Gxe2x80x94 is 
in which
r is 0, 1 or 2;
Rg is (C1-C6)alkyl, (C3-C8)cycloalkyl, or xe2x80x94(CH2)pxe2x80x94Lxe2x80x94(CH2)qxe2x80x94Txe2x80x2;
Rp is (C1-C6)alkyl, (C3-C8)cycloalkyl, or xe2x80x94(CH2)pxe2x80x94Lxe2x80x94(CH2)qxe2x80x94Txe2x80x2;
where p is 0, 1, 2, 3, or 4; L is a bond, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, or xe2x80x94NHxe2x80x94; q is 0, 1, 2 or 3; and Txe2x80x2 is (C1-C4)alkyl, (C3-C8)cycloalkyl, xe2x80x94COOH, xe2x80x94CONH2, or Ar, where Ar is unsubstituted or substituted aryl, where aryl is phenyl, naphthyl, a 5- or 6-membered unsubstituted or substituted aromatic heterocyclic ring, having one or two heteroatoms which are the same or different and which are selected from sulfur, oxygen and nitrogen, or a 9- or 10-membered unsubstituted or substituted fused bicyclic aromatic heterocyclic group having one or two heteroatoms which are the same or different and which are selected from sulfur, oxygen and nitrogen;
Ry is xe2x80x94CH2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, or xe2x80x94NHxe2x80x94; and
Rz is a bond or, when taken with Ry and the three adjoining carbon atoms, forms a saturated carbocyclic ring of 5-8 atoms, one atom of which may be xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, or xe2x80x94NHxe2x80x94;
xe2x80x94Gxe2x80x94R is xe2x80x94C(O)xe2x80x94NHxe2x80x94(CH2)sxe2x80x94R, xe2x80x94CH2xe2x80x94NHxe2x80x94(CH2)sxe2x80x94R, xe2x80x94CH2xe2x80x94NHxe2x80x94C(O)xe2x80x94R or xe2x80x94(CH2)txe2x80x94Oxe2x80x94R in which s is 1 or 2 and t is 1, 2 or 3; and
R is a 4-amidino-3-hydroxyphenyl group bearing 0, 1, 2 or 3 fluoro substituents;
or a pharmaceutically acceptable salt thereof.
In addition to a compound of Formula I, the present invention provides a pharmaceutical composition comprising a compound of Formula I, or a pharmaceutically acceptable salt thereof, in association with a pharmaceutically acceptable carrier, diluent or excipient.
The present invention further provides a method of inhibiting thrombin comprising administering to a mammal in need of treatment, a thrombin inhibiting dose of a compound of Formula I.
The present invention also provides a method of inhibiting thrombosis in a mammal comprising administering to a mammal in need of treatment, an antithrombotic dose of a compound of Formula I.
This invention relates to new inhibitors of thrombin, pharmaceutical compositions containing the compounds as active ingredients, and the use of the compounds as anticoagulants for prophylaxis and treatment of thromboembolic diseases such as venous thrombosis, pulmonary embolism, arterial thrombosis, in particular myocardial ischemia, myocardial infarction and cerebral thrombosis, general hypercoagulable states and local hypercoagulable states, such as following angioplasty and coronary bypass operations, and generalized tissue injury as it relates to the inflammatory process.
In this specification, the following definitions are used, unless otherwise described: Halo is fluoro, chloro, bromo or iodo. Alkyl, alkoxy, etc. denote both straight and branched groups; but reference to an individual radical such as xe2x80x9cpropylxe2x80x9d embraces only the straight chain (xe2x80x9cnormalxe2x80x9d) radical, a branched chain isomer such as xe2x80x9cisopropylxe2x80x9d being specifically denoted.
The term xe2x80x9c5- or 6-membered aromatic heterocyclic ringxe2x80x9d means any 5- or 6-membered ring that will afford a stable structure containing one or two nitrogen atoms; one sulfur atom; one oxygen atom; one nitrogen and one sulfur atom; or one nitrogen and one oxygen atom. The 5-membered ring has two double bonds and the 6-membered ring has three double bonds.
The term xe2x80x9c9- or 10-membered fused bicyclic aromatic heterocyclic groupxe2x80x9d means any bicyclic group in which any of the above 5- or 6-membered rings is ortho fused to a benzene ring or to a 6-membered heterocyclic aromatic ring as defined above in a manner that will afford a stable structure.
It will be appreciated that many of the above heterocycles may exist in tautomeric forms. All such forms are included within the scope of this invention.
Each of the aromatic or heteroaromatic groups listed for the definition of Ar or Rxe2x80x3 is independently unsubstituted or substituted with one or two substituents that will afford a stable structure independently selected from halo, hydroxy, (C1-C4)alkyl, (C1-C4)alkoxy, amino, mono(C1-C4 alkyl)amino, di(C1-C4 alkyl)amino, -(CH2)jCOOH, mercapto, xe2x80x94S(O)h(C1-C4 alkyl), xe2x80x94NHS(O)h(C1-C4 alkyl), xe2x80x94NHC(O)(C1-C4 alkyl), xe2x80x94S(O)hNH2, xe2x80x94S(O)hNH(C1-C4 alkyl), or xe2x80x94S(O)hN(C1-C4 alkyl)2, h is 0, 1 or 2, and j is 0, 1, 2, 3, or 4.
In the representation of Formula I, the carbonyl functionality of group Xxe2x80x94(CO)xe2x80x94 is attached to the amine functionality of the xe2x80x94Yxe2x80x94 group.
The group 
where Z and A are both hydrogen, is referred to at times herein as phenylglycyl and abbreviated Phg. Compounds wherein A is, e.g., methyl, are referred to as the Nxcex1-methyl-phenylglycyl group and abbreviated MePhg. Substituted compounds wherein Z is other than hydrogen are referred to by the type and position of the substituent group, e.g., 3xe2x80x2-chlorophenylglycyl or Phg(3-Cl).
The group 
where Z and A are both hydrogen, is referred to at times herein as phenylalanyl and abbreviated Phe. Compounds wherein A is, e.g., methyl, are referred to as the Nxcex1-methyl-phenylalanyl group and abbreviated MePhe. Substituted compounds wherein Z is other than hydrogen are referred to by the type and position of the substituent group, e.g., 3xe2x80x2-chlorophenylalanyl or Phe(3-Cl).
The groups 
when Rxe2x80x2 is hydrogen, are referred to at times herein as 1- and 3-tetrahydro-isoquinolinecarbonyl, respectively, and are respectively abbreviated 1-Tiq and 3-Tiq.
The groups 
when Rxe2x80x2 is hydrogen, are referred to at times herein as 1- and 3-perhydro-isoquinolinecarbonyl, respectively, and are respectively abbreviated 1-Piq and 3-Piq. As indicated by the crooked lines, various ring fusion isomers of these substituents existxe2x80x94this invention contemplates any individual isomer and combinations thereof.
The group 
wherein r is 0, 1, or 2 is referred to as azetidine-2-carbonyl, prolinyl, or homoprolinyl, and is abbreviated Azt, Pro or hPro, respectively.
The group 
represents a saturated bicyclic system of the 4,5; 5,5; 6,5; 7,5; or 8,5 type. The stereochemistry at 3a is cis to the carbonyl; the other bridgehead bond may be either cis or trans except that the 4,5 and 5,5 systems must be cis at the bridgehead. The definitions of Ry and Rz provide that the variable ring, which includes the three carbon atoms shown, is a saturated carbocyclic system of 4-8 atoms. All of the ring atoms may be carbon, or one of the ring atoms may be a hetero atom selected from xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, and xe2x80x94NHxe2x80x94. This definition includes the moiety derived from octahydroindole-2-carboxylic acid, as represented by 
The various cis and trans forms of this moiety are contemplated by this invention. The preferred isomer derived from [2S-(2xcex1,3axcex2,7axcex2)]-octahydro-indole-2-carboxylic acid is abbreviated xe2x80x9cOhixe2x80x9d and is represented by 
The asterisks in radical Y denote a chiral center that corresponds to (L) in the natural amino acids. The asterisk in radical X denotes a chiral center that is (D) or (DL); the # in radical X denotes a chiral center that is (L).
It will be appreciated that certain compounds of Formula I may exist in, and be isolated in, isomeric forms, including tautomeric forms or cis- or trans-isomers, as well as optically active racemic or diastereomeric forms. The present invention encompasses a compound of Formula I in any of the tautomeric forms or as a mixture thereof. It is to be understood that the present invention encompasses a compound of Formula I as a mixture of diastereomers, as well as in the form of an individual diastereomer, and that the present invention encompasses a compound of Formula I as a mixture of enantiomers, as well as in the form of an individual enantiomer, any of which mixtures or form possesses inhibitory properties against thrombin, it being well known in the art how to prepare or isolate particular forms and how to determine inhibitory properties against thrombin by standard tests including those described below.
In addition, a compound of Formula I may exhibit polymorphism or may form a solvate with water or an organic solvent. The present invention also encompasses any such polymorphic form, any solvate or any mixture thereof.
Particular values are listed below for radicals (either alone or as part of another radical), substituents, and ranges, for illustration only, and they do not exclude other defined values or other values within defined ranges for the radicals and substituents.
A particular value for a (C1-C4)alkyl group, a (C1-C6)alkyl group, a (C1-C8)alkyl group or a (C1-C10)alkyl group is methyl, ethyl, propyl, isopropyl, butyl, isobutyl or t-butyl. A particular value for a (C1-C4)alkoxy group is methoxy, ethoxy, propoxy, isopropoxy, or t-butyloxy. A particular value for a (C3-C8)cycloalkyl group is cyclopropyl, cyclopentyl or cyclohexyl. A particular value for a (C1-C4)fluoroalkyl group is trifluoromethyl or 2,2,2-trifluoroethyl. A particular value for aryl is phenyl, naphthyl, furyl, thienyl, pyridyl, indolyl, quinolinyl or isoquinolinyl.
A particular compound of Formula I as defined above is one in which
Xxe2x80x94C(O)xe2x80x94 is D-homoprolinyl, 
in which T is cyclohexyl or phenyl; a is 0 or 1; and A is hydrogen, (C1-C4)alkyl, (C1-C4 alkyl)sulfonyl, (C1-C4 alkyl)-oxy-carbonyl, (C1-C4 alkyl)carbonyl or carboxymethyl; and
xe2x80x94Yxe2x80x94Gxe2x80x94 is xe2x80x94NRgxe2x80x94CH2xe2x80x94Gxe2x80x94, 
in which Rg is (C1-C6)alkyl, xe2x80x94(CH2)qxe2x80x94(C3-C8)cycloalkyl or xe2x80x94(CH2)q-phenyl; q is 0, 1, 2 or 3; and r is 0, 1, or 2;
or a pharmaceutically acceptable salt thereof.
A preferred compound of Formula I as defined above is one in which 
wherein T is cyclohexyl; a is 1; and A is hydrogen, ethylsulfonyl or carboxymethyl, particularly carboxymethyl; and 
in which r is 0 or 1;
or a pharmaceutically acceptable salt thereof.
For any of the above defined compounds of Formula I, a particular value of xe2x80x94Gxe2x80x94R is xe2x80x94C(O)xe2x80x94NHxe2x80x94(CH2)sxe2x80x94R; and a preferred value of xe2x80x94Gxe2x80x94R is xe2x80x94C(O)xe2x80x94NHxe2x80x94(CH2)sxe2x80x94R in which s is 1, i.e. xe2x80x94C(O)xe2x80x94NHxe2x80x94CH2xe2x80x94R.
A particular compound of Formula I in which xe2x80x94Gxe2x80x94R is xe2x80x94C(O)xe2x80x94NHxe2x80x94CH2xe2x80x94R and the other groups have any of the above definitions may be denoted by Formula Ia 
in which f is 0, 1, 2 or 3.
For any of the above defined compounds of Formula I, a particular value for R is 4-amidino-3-hydroxyphenyl or 4-amidino-3-hydroxy-2,5,6-trifluorophenyl; and a more particular value is 4-amidino-3-hydroxyphenyl.
A particular compound of the invention is one of those described herein as Example 1, 2, 3, 4, 5, 9, 10 or 11; and a preferred compound is one described as Example 1, 3 or 5, particularly Example 3; or a pharmaceutically acceptable salt thereof.
A compound of Formula I may be made by processes which include processes known in the chemical art for the production of structurally analogous compounds or by a novel process described herein. Novel processes and intermediates for the manufacture of a compound of Formula I as defined above provide further features of the invention and are illustrated by the following procedures in which the meanings of the generic radicals are as defined above, unless otherwise specified. It will be recognized that it may be preferred or necessary to prepare a compound of Formula I in which a functional group is protected using a conventional protecting group, then to remove the protecting group to provide the compound of Formula I.
(A) For a compound of Formula I in which xe2x80x94Gxe2x80x94R is xe2x80x94C(O) xe2x80x94Nxe2x80x94(CH2)sxe2x80x94R, coupling an acid of Formula II,
Xxe2x80x94C(O)xe2x80x94Yxe2x80x94C(O)xe2x80x94OH xe2x80x83xe2x80x83II 
or an activated derivative thereof, with an amine of Formula III.
H2Nxe2x80x94(CH2)sxe2x80x94R xe2x80x83xe2x80x83III 
The coupling is carried out using a conventional procedure, for example by using a coupling reagent such as benzotriazol-1-yloxytripyrrolidinophosphonium hexafluorophosphate, for example as described in Example 1-E, or such as 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, for example as described in Example 5.
(B) Coupling an acid of Formula IV,
Xxe2x80x94C(O)xe2x80x94OH xe2x80x83xe2x80x83IV 
or an activated derivative thereof, with an amine of Formula V.
Hxe2x80x94Yxe2x80x94Gxe2x80x94R xe2x80x83xe2x80x83V 
The coupling is carried out using a conventional procedure, such as by using one of the methods described above in (A).
(C) Hydrogenolyzing the N-O bond of a corresponding compound of Formula VI 
in which f is 0, 1, 2 or 3. Conveniently, the hydrogenolysis is carried out using a palladium on carbon catalyst in acidic, aqueous alchohol at ambient temperature and under hydrogen at ambient or a few bars"" pressure; and the product is isolated as its acid addition salt.
Whereafter, for any of the above procedures, when a functional group is protected using a protecting group, removing the protecting group.
Whereafter, for any of the above procedures, when a pharmaceutically acceptable salt of a compound of Formula I is required, it is obtained by reacting the acidic or basic form of such a compound of Formula I with a base or an acid affording a physiologically acceptable counterion or by any other conventional procedure, such as, for example, exchanging the counterion of a salt.
A compound corresponding to compound of Formula I in which one or more functional groups is protected provides another aspect of the invention. Such a compound may be represented as a compound of Formula Ip
(PX)Xxe2x80x94C(O)xe2x80x94(PY)Yxe2x80x94G(PG)xe2x80x94R(PR) xe2x80x83xe2x80x83Ip 
which bears one or more of the protecting groups PX, PY, PG and PR wherein PX is an optional protecting group(s) for a functional group(s) of Xxe2x80x94C(O)xe2x80x94; PY is an optional protecting group(s) for a functional group(s) of xe2x80x94Yxe2x80x94; PG is an optional amino protecting group for G when G-R is xe2x80x94(CH2)xe2x80x94NHxe2x80x94(CH2)sxe2x80x94R; and PR is an optional protecting group(s) for a functional group of R. Typical values for PX and PY include the groups which form a t-butylester or benzyl ester when the protected functional group is carboxy, the groups which form a t-butyl urethane or a benzyl urethane when the protected functional group is amino, and the groups which form a methyl ether, t-butyl ether or benzyl ether when the protected functional group is hydroxy. It will be recognized that some compounds of Formula I may serve as a protected equivalent of another compound of Formula I. For example, a compound of Formula I in which A is Rxe2x80x3OC(O)xe2x80x94 wherein Rxe2x80x3 is t-butyl is a protected equivalent of a compound of Formula I in which A is hydrogen, as described in Example 1. Similarly, a compound of Formula I in which Rm is xe2x80x94COORb wherein Rb t-butyl is a protected equivalent of a compound of Formula I in which Rm is xe2x80x94COORb and Rb is hydrogen.
As mentioned above, the invention includes a pharmaceutically acceptable salt of a thrombin inhibiting compound defined by the above Formula I. A particular benzamidine of this invention possesses one or more sufficiently basic functional groups to react with any of a number of nontoxic inorganic and organic acids to form a pharmaceutically acceptable salt. Acids commonly employed to form acid addition salts are inorganic acids such as hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, phosphoric acid, and the like, and organic acids such as p-toluene sulfonic, methanesulfonic acid, oxalic acid, p-bromo phenyl sulfonic acid, carbonic acid, succinic acid, citric acid, benzoic acid, acetic acid, and the like. Examples of such pharmaceutically acceptable salts thus are the sulfate, pyrosulfate, bisulfate, sulfite, bisulfite, phosphate, monohydrogenphosphate, dihydrogenphosphate, metaphosphate, pyrophosphate, chloride, bromide, iodide, acetate, propionate, decanoate, caprylate, acrylate, formate, isobutyrate, caproate, heptanoate, propiolate, oxalate, malonate, succinate, suberate, sebacate, fumarate, maleate, butyne-1,4-dioate, hexyne-1,6-dioate, benzoate, chlorobenzoate, methylbenzoate, dinitrobenzoate, hydroxybenzoate, methoxybenzoate, phthalate, sulfonate, xylenesulfonate, phenylacetate, phenylpropionate, phenylbutyrate, citrate, lactate, gamma-hydroxybutyrate, glycollate, tartrate, methanesulfonate, propanesulfonate, naphthalene-1-sulfonate, naphthalene-2-sulfonate, mandelate, and the like. Preferred pharmaceutically acceptable acid addition salts include those formed with mineral acids such as hydrochloric acid, hydrobromic acid and sulfuric acid.
For a compound of Formula I in which X or Y bears an acidic moiety, such a a carboxy group, a pharmaceutically acceptable salt may be made with a base which affords a pharmaceutically acceptable cation, which includes alkali metal salts (especially sodium and potassium), alkaline earth metal salts (especially calcium and magnesium), aluminum salts and ammonium salts, as well as salts made from physiologically acceptable organic bases such as triethylamine, morpholine, piperidine and triethanolamine.
If not commercially available, the necessary starting materials for the preparation of a compound of Formula I may be prepared by procedures which are selected from standard techniques of organic chemistry, including aromatic and heteroaromatic substitution and transformation, from techniques which are analogous to the syntheses of known, structurally similar compounds, especially peptide syntheses, and techniques which are analogous to the above described procedures or procedures described in the Examples. It will be clear to one skilled in the art that a variety of sequences is available for the preparation of the starting materials. Starting materials and procedures which are novel provide further aspects of the invention.
A starting material acid of Formula II also may be represented as an acid of Formula IIp
(PX)Xxe2x80x94C(O)xe2x80x94(PY)Yxe2x80x94C(O)xe2x80x94OH xe2x80x83xe2x80x83IIp 
in which PX and PY are optional protecting groups as defined above. Conveniently, an acid of Formula IIp may be prepared by coupling an optionally protected acid of Formula VII
(PX)Xxe2x80x94C(O)xe2x80x94OH xe2x80x83xe2x80x83VII 
with an amino acid derivative of Formula VIII
Hxe2x80x94(PY)Yxe2x80x94C(O)xe2x80x94OPC xe2x80x83xe2x80x83VIII 
in which PC is hydrogen or a carboxy protecting group, such as for example methyl, ethyl, t-butyl or benzyl, followed by removal of the protecting group PC, when present.
A convenient general route for the preparation of an amine of Formula III or an amine of Formula V is outlined in Scheme I, in which Ga represents a latent or protected form of the group H2Nxe2x80x94(CH2)sxe2x80x94 or the group Hxe2x80x94Yxe2x80x94Gxe2x80x94, respectively, and f is 0, 1, 2 or 3. 
Thus, according to the method of Shutske and Kapples (J. Heterocyclic Chem. (1989), 26, 1293-1298), an ortho-fluoro benzonitrile of Formula X is treated with the potassium anion of acetone oxime to afford the corresponding oxime of Formula XI; acid hydrolysis of the oxime affords the amine of Formula XII which cyclizes in situ to afford the substituted 3-amino-1,2-benzisoxazole derivative of Formula XIII. The group Ga may be converted into H2Nxe2x80x94(CH2)sxe2x80x94 to afford an amine of Formula XIV or into Hxe2x80x94Yxe2x80x94G to afford an amine of Formula XV, respectively; hydrogenolysis of the benzisoxazole, using a procedure similar to that described in (C) above, then affords the respective amine of Formula III or Formula V. Alternatively, it may be preferred to first hydrogenolyze the benzisoxazole of Formula XIII to a corresponding compound of Formula XVI before transforming the group Ga to afford an amine of Formula III or Formula V. As described at Example 1-D and at Example 2-B, the conversion of Ga (as cyano) into H2Nxe2x80x94CH2xe2x80x94 may be performed at the same time as the hydrogenolysis, thus providing a xe2x80x9cone-potxe2x80x9d conversion of a compound of Formula XIII into an amine of Formula III.
A starting material of Formula VI may be prepared by a route analogous to one described above, for example by using a compound of Formula XIV or Formula XV, or a protected derivative thereof.
A compound of the invention is isolated best in the form of an acid addition salt. A salt of the compound of Formula I formed with an acid such as one of those mentioned above is useful as a pharmaceutically acceptable salt for administration of the antithrombotic agent and for preparation of a formulation of the agent. Other acid addition salts may be prepared and used in the isolation and purification of the compound.
One of the novel intermediates of the invention is a compound of Formula III, or a salt and/or protected derivative thereof. A particular compound of Formula III is one in which s is 1 and which may be represented by Formula IIIa 
in which f is 0, 1, 2 or 3. A particular compound of Formula IIIa is one in which f is 0 or 3.
An additional aspect of the invention is the use of a compound of Formula III (or Formula IIIa) as defined above, or a salt or protected derivative thereof, as a starting material in the synthesis of a thrombin inhibitor.
As another aspect of the invention, there is provided a novel structural fragment of the formula 
wherein f is 0, 1, 2 or 3 (particularly f is 0 or 3) as a novel structural element in a thrombin inhibitor, particularly in a peptidomimetic thrombin inhibitor.
Another novel intermediate of the invention is a compound of Formula XIII in which Ga is cyano and which may be represented by Formula XIIIa 
wherein f is 0, 1, 2 or 3; particularly wherein f is 0 or 3.
As noted above, the optically active isomers and diastereomers of the compounds of Formula I are also considered part of this invention. Such optically active isomers may be prepared from their respective optically active precursors by the procedures described above, or by resolving the racemic mixtures. This resolution can be carried out by derivatization with a chiral reagent followed by chromatography or by repeated crystallization. Removal of the chiral auxiliary by standard methods affords substantially optically pure isomers of the compounds of the present invention or their precursors. Further details regarding resolutions can be obtained in Jacques, et al., Enantiomers, Racemates, and Resolutions, John Wiley and Sons, 1981.
The compounds of the invention are believed to selectively inhibit thrombin over other proteinases and nonenzyme proteins involved in blood coagulation without appreciable interference with the body""s natural clot lysing ability (the compounds have a low inhibitory effect on fibrinolysis). Also, they generally exhibit increased selectivity for thrombin compound to the prior amidinophenyl compounds. Further, such selectivity is believed to permit use with thrombolytic agents without substantial interference with thrombolysis and fibrinolysis.
The invention in one of its aspects provides a method of inhibiting thrombin in mammals comprising administering to a mammal in need of treatment an effective (thrombin inhibiting) dose of a compound of Formula I.
In another of its aspects, the invention provides a method of treating a thromboembolic disorder comprising administering to a mammal in need of treatment an effective (thromboembolic disorder therapeutic and/or prophylactic amount) dose of a compound of Formula I.
The invention in another of its aspects provides a method of inhibiting coagulation in a mammal comprising administering to a mammal in need of treatment an effective (coagulation inhibiting) dose of a compound of Formula I.
The thrombin inhibition, coagulation inhibition and thromboembolic disorder treatment contemplated by the present method includes both medical therapeutic and/or prophylactic treatment as appropriate.
In a further embodiment the invention relates to treatment, in a human or other mammal, of conditions where inhibition of thrombin is required. The compounds of the invention are expected to be useful in mammals, including man, in treatment or prophylaxis of thrombosis and hypercoagulability in blood and tissues. Disorders in which the compounds have a potential utility are in treatment or prophylaxis of thrombosis and hypercoagulability in blood and tissues. Disorders in which the compounds have a potential utility, in treatment and/or prophylaxis, include venous thrombosis and pulmonary embolism, arterial thrombosis, such as in myocardial ischemia, myocardial infarction, unstable angina, thrombosis-based stroke and peripheral arterial thrombosis. Further, the compounds have expected utility in the treatment or prophylaxis of atherosclerotic disorders (diseases) such as coronary arterial disease, cerebral arterial disease and peripheral arterial disease. Further, the compounds are expected to be useful together with thrombolytics in myocardial infarction. Further, the compounds have expected utility in prophylaxis for reocclusion after thrombolysis, percutaneous transluminal angioplasty (PTCA) and coronary bypass operations. Further, the compounds have expected utility in prevention of rethrombosis after microsurgery. Further, the compounds are expected to be useful in anticoagulant treatment in connection with artificial organs and cardiac valves. Further, the compounds have expected utility in anticoagulant treatment in hemodialysis and disseminated intravascular coagulation. A further expected utility is in rinsing of catheters and mechanical devices used in patients in vivo, and as an anticoagulant for preservation of blood, plasma and other blood products in vitro. Still further, the compounds have expected utility in other diseases where blood coagulation could be a fundamental contributing process or a source of secondary pathology, such as cancer, including metastasis, inflammatory diseases, including arthritis, and diabetes. The anti-coagulant compound is administered orally, parenterally e.g. by intravenous infusion (iv), intramuscular injection (im) or subcutaneously (sc).
The specific dose of a compound administered according to this invention to obtain therapeutic and/or prophylactic effects will, of course, be determined by the particular circumstances surrounding the case, including, for example, the compound administered, the rate of administration, the route of administration, and the condition being treated.
A typical daily dose for each of the above utilities is between about 0.01 mg/kg and about 1000 mg/kg. The dose regimen may vary e.g. for prophylactic use a single daily dose may be administered or multiple doses such as 3 or 5 times daily may be appropriate. In critical care situations a compound of the invention is administered by iv infusion at a rate between about 0.01 mg/kg/h and about 20 mg/kg/h and preferably between about 0.1 mg/kg/h and about 5 mg/kg/h.
The method of this invention also is practiced in conjunction with a clot lysing agent e.g. tissue plasminogen activator (t-PA), modified t-PA, streptokinase or urokinase. In cases when clot formation has occurred and an artery or vein is blocked, either partially or totally, a clot lysing agent is usually employed. A compound of the invention can be administered prior to or along with the lysing agent or subsequent to its use, and preferably further is administered along with aspirin to prevent the reoccurrence of clot formation.
The method of this invention is also practiced in conjunction with a platelet glycoprotein receptor (IIb/IIIa) antagonist, that inhibits platelet aggregation. A compound of the invention can be administered prior to or along with the IIb/IIIa antagonist or subsequent to its use to prevent the occurrence or reoccurrence of clot formation.
The method of this invention is also practiced in conjunction with aspirin. A compound of the invention can be administered prior to or along with aspirin or subsequent to its use to prevent the occurrence or reoccurrence of clot formation. As stated above, preferably a compound of the present invention is administered in conjunction with a clot lysing agent and aspirin.
This invention also provides pharmaceutical compositions for use in the above described therapeutic method. Pharmaceutical compositions of the invention comprise an effective thrombin inhibiting amount of a compound of formula I in association with a pharmaceutically acceptable carrier, excipient or diluent. For oral administration the antithrombotic compound is formulated in gelatin capsules or tablets which may contain excipients such as binders, lubricants, disintegration agents and the like. For parenteral administration the antithrombotic is formulated in a pharmaceutically acceptable diluent e.g. physiological saline (0.9 percent), 5 percent dextrose, Ringer""s solution and the like.
The compound of the present invention can be formulated in unit dosage formulations comprising a dose between about 0.1 mg and about 1000 mg. Preferably the compound is in the form of a pharmaceutically acceptable salt such as for example the sulfate salt, acetate salt or a phosphate salt. An example of a unit dosage formulation comprises 5 mg of a compound of the present invention as a pharmaceutically acceptable salt in a 10 ml sterile glass ampoule. Another example of a unit dosage formulation comprises about 10 mg of a compound of the present invention as a pharmaceutically acceptable salt in 20 ml of isotonic saline contained in a sterile ampoule.
The compounds can be administered by a variety of routes including oral, rectal, transdermal, subcutaneous, intravenous, intramuscular, and intranasal. The compounds of the present invention are preferably formulated prior to administration. Another embodiment of the present invention is a pharmaceutical composition comprising an effective amount of a compound of Formula I or a pharmaceutically acceptable salt or solvate thereof in association with a pharmaceutically acceptable carrier, diluent or excipient therefor.
The active ingredient in such formulations comprises from 0.1 percent to 99.9 percent by weight of the formulation. By xe2x80x9cpharmaceutically acceptablexe2x80x9d it is meant the carrier, diluent or excipient must be compatible with the other ingredients of the formulation and not deleterious to the recipient thereof.
The present pharmaceutical compositions are prepared by known procedures using well known and readily available ingredients. The compositions of this invention may be formulated so as to provide quick, sustained, or delayed release of the active ingredient after administration to the patient by employing procedures well known in the art. In making the compositions of the present invention, the active ingredient will usually be admixed with a carrier, or diluted by a carrier, or enclosed within a carrier which may be in the form of a capsule, sachet, paper or other container. When the carrier serves as a diluent, it may be a solid, semi-solid or liquid material which acts as a vehicle, excipient or medium for the active ingredient. Thus, the compositions can be in the form of tablets, pills, powders, lozenges, sachets, cachets, elixirs, suspensions, emulsions, solutions, syrups, aerosols, (as a solid or in a liquid medium), soft and hard gelatin capsules, suppositories, sterile injectable solutions, sterile packaged powders, and the like.
The following formulation examples are illustrative only and are not intended to limit the scope of the invention in any way. xe2x80x9cActive ingredient,xe2x80x9d of course, means a compound according to Formula I or a pharmaceutically acceptable salt or solvate thereof.
Formulation 1: Hard gelatin capsules are prepared using the following ingredients:
Formulation 2: A tablet is prepared using the ingredients below:
The components are blended and compressed to form tablets each weighing 665 mg.
Formulation 3: An aerosol solution is prepared containing the following components:
The active compound is mixed with ethanol and the mixture added to a portion of the propellant 22, cooled to xe2x88x9230xc2x0 C. and transferred to a filling device. The required amount is then fed to a stainless steel container and diluted with the remainder of the propellant. The valve units are then fitted to the container.
Formulation 4: Tablets, each containing 60 mg of active ingredient, are made as follows:
The active ingredient, starch and cellulose are passed through a No. 45 mesh U.S. sieve and mixed thoroughly. The aqueous solution containing polyvinylpyrrolidone is mixed with the resultant powder, and the mixture then is passed through a No. 14 mesh U.S. sieve. The granules so produced are dried at 50xc2x0 C. and passed through a No. 18 mesh U.S. Sieve. The sodium carboxymethyl starch, magnesium stearate and talc, previously passed through a No. 60 mesh U.S. sieve, are then added to the granules which, after mixing, are compressed on a tablet machine to yield tablets each weighing 150 mg.
Formulation 5: Capsules, each containing 80 mg of active ingredient, are made as follows:
The active ingredient, cellulose, starch, and magnesium stearate are blended, passed through a No. 45 mesh U.S. sieve, and filled into hard gelatin capsules in 200 mg quantities.
Formulation 6: Suppositories, each containing 225 mg of active ingredient, are made as follows:
The active ingredient is passed through a No. 60 mesh U.S. sieve and suspended in the saturated fatty acid glycerides previously melted using the minimum heat necessary. The mixture is then poured into a suppository mold of nominal 2 g capacity and allowed to cool.
Formulation 7: Suspensions, each containing 50 mg of active ingredient per 5 ml dose, are made as follows:
The active ingredient is passed through a No. 45 mesh U.S. sieve and mixed with the sodium carboxymethyl cellulose and syrup to form a smooth paste. The benzoic acid solution, flavor and color are diluted with a portion of the water and added, with stirring. Sufficient water is then added to produce the required volume.
Formulation 8: An intravenous formulation may be prepared as follows:
The solution of the above ingredients generally is administered intravenously to a subject at a rate of 1 ml per minute.
The ability of a compound of the present invention to be an effective and orally active thrombin inhibitor is evaluated in one or more of the following assays.
The compounds provided by the invention (Formula I) selectively inhibit the action of thrombin in mammals. The inhibition of thrombin is demonstrated by in vitro inhibition of the amidase activity of thrombin as measured in an assay in which thrombin hydrolyzes the chromogenic substrate, N-benzoyl-L-phenylalanyl-L-valyl-L-arginyl-p-nitroanilide, N-benzoyl-L-Phe-L-Val-L-Arg-p-nitroanilide.
The assay is carried out by mixing 50 xcexcl buffer (0.03M Tris, 0.15M NaCl, pH 7.4) with 25 xcexcl of human thrombin solution (purified human thrombin, Enzyme Research Laboratories, South Bend, Ind., at 8 NIH units/ml) and 25 xcexcl of test compound in a solvent (50% aqueous methanol (v:v)). Then 150 xcexcl of an aqueous solution of the chromogenic substate (at 0.25 mg/ml) are added and the rates of hydrolysis of the substrate are measured by monitoring the reactions at 405 nm for the release of p-nitroaniline. Standard curves are constructed by plotting free thrombin concentration against hydrolysis rate. The hydrolysis rates observed with test compounds are then converted to xe2x80x9cfree thrombinxe2x80x9d values in the respective assays by use of the standard curves. The bound thrombin (bound to test compound) is calculated by subtracting the amount of free thrombin observed in each assay from the known initial amount of thrombin used in the assay. The amount of free inhibitor in each assay is calculated by subtracting the number of moles of bound thrombin from the number of moles of added inhibitor (test compound).
The Kass value is the hypothetical equilibrium constant for the reaction between thrombin and the test compound (I).       Thrombin    +                  I        ⁢                  xe2x80x83                ⁢                  ⟵          ⟶                ⁢                  xe2x80x83                ⁢        Thrombin            ⁢              -            ⁢      I            Kass    =                  [                  Thrombin          ⁢                      -                    ⁢          I                ]                    [                              (            Thrombin            )                    xc3x97                      (            I            )                          ]            
Kass is calculated for a range of concentrations of test compounds and the mean value reported in units of liter per mole. In general, a thrombin inhibiting compound of Formula I of the instant invention exhibits a Kass of 0.1xc3x97106 L/mole or much greater. For example, each of the particularly preferred examples of the invention listed above was determined to have a Kass of at least 100xc3x97106 L/mole. Thus, the compounds of Examples 1, 3 and 5 were found to have a Kass of 770xc3x97106 L/mole, 1,200xc3x97106 L/mole and 100xc3x97106 L/mole, respectively.
By substantially following the procedures described above for human thrombin, and using other human blood coagulation system serine proteases and using fibrinolytic system serine proteases, with the appropriate chromogenic substrates, identified below, the selectivity of the compounds of the present invention with respect to the coagulation factor serine proteases and to the fibronolytic serine proteases are evaluated as well as their substantial lack of interference with human plasma clot fibrinolysis.
Human factors X, Xa, IXa, XIa, and XIIa are purchased from Enzyme Research Laboratories, South Bend, Ind.; human urokinase from Leo Pharmaceuticals, Denmark; and recombinant activated Protein C (aPC) is prepared at Eli Lilly and Co. substantially according to U.S. Pat. No. 4,981,952. Chromogenic substrates: N-Benzoyl-Ile-Glu-Gly-Arg-p-nitroanilide (for factor Xa); N-Cbz-D-Arg-Gly-Arg-p-nitroanilide (for factor IXa assay as the factor Xa substrate); Pyroglutamyl-Pro-Arg-p-nitroanilide (for Factor XIa and for aPC); H-D-Pro-Phe-Arg-p-nitroanilide (for factor XIIa); and Pyroglutamyl-Gly-Arg-p-nitroanilide (for urokinase); are purchased from Kabi Vitrum, Stockholm, Sweden, or from Midwest Biotech, Fishers, Ind. Bovine trypsin is purchased from Worthington Biochemicals, Freehold, N.J., and human plasma kallikrein from Kabi Vitrum, Stockholm, Sweden. Chromogenic substrate H-D-Pro-Phe-Arg-p-nitroanilide for plasma kallikrein is purchased from Kabi Vitrum, Stockholm, Sweden. N-Benzoyl-Phe-Val-Arg-p-nitroanilide, the substrate for human thrombin and for trypsin, is synthesized according to procedures described above for the compounds of the present invention, using known methods of peptide coupling from commercially available reactants, or purchased from Midwest Biotech, Fishers, Ind.
Human plasmin is purchased from Boehringer Mannheim, Indianapolis, Ind.: nt-PA is purchased as single chain activity reference from American Diagnostica, Greenwich, Conn.; modified-t-PA6 (mt-PA6) is prepared at Eli Lilly and Company by procedure known in the art (See, Burck, et al., J. Biol. Chem., 265, 5120-5177 (1990). Plasmin chromogenic substrate H-D-Val-Leu-Lys-p-nitroanilide and tissue plasminogen activator (t-PA) substrate H-D-Ile-Pro-Arg-p-nitroanilide are purchased from Kabi Vitrum, Stockholm, Sweden.
In the chromogenic substrates described above the three-letter symbols Ile, Glu, Gly, Pro, Arg, Phe, Val, Leu and Lys are used to indicate the corresponding amino acid group isoleucine, glutamic acid, glycine, proline, arginine, phenylalanine, valine, leucine and lysine, respectively.
Thrombin inhibitors preferably should spare fibrinolysis induced by urokinase, tissue plasminogen activator (t-PA) and steptokinase. This would be important to the therapeutic use of such agents as an adjunct to streptokinase, t-PA or urokinase thrombolytic therapy and to the use of such agents as an endogenous fibrinolysis-sparing (with respect to t-PA and urokinase) antithrombotic agents. In addition to the lack of interference with the amidase activity of the fibrinolytic proteases, such fibrinolytic system sparing can be studied by the use of human plasma clots and their lysis by the respective fibrinolytic plasminogen activators.
Materials
Dog plasma is obtained from conscious mixed-breed hounds (either sex Hazelton-LRE, Kalamazoo, Mich., U.S.A.) by venipuncture into 3.8 percent citrate. Fibrinogen is prepared from fresh dog plasma and human fibrinogen is prepared from in-date ACD human blood at the fraction I-2 according to previous procedures and specifications. Smith, Biochem. J., 185, 1-11 (1980); and Smith, et al., Biochemistry, 11, 2958-2967, (1972). Human fibrinogen (98 percent pure/plasmin free) is from American Diagnostica, Greenwich, Conn. Radiolabeling of fibrinogen I-2 preparations is performed as previously reported. Smith, et al., Biochemistry, 11, 2958-2967, (1972). Urokinase is purchased form Leo Pharmaceuticals, Denmark, as 2200 Ploug units/vial. Streptokinase is purchased from Hoechst-Roussel Pharmaceuticals, Somerville, N.J.
Methodsxe2x80x94Effects on Lysis of Human Plasma Clots by t-PA
Human plasma clots are formed in micro test tubes by adding 50 xcexcl thrombin (73 NIH unit/ml) to 100 xcexcl human plasma which contains 0.0229 xcexcCi 125-iodine labeled fibrinogen. Clot lysis is studied by overlaying the clots with 50 xcexcl of urokinase or streptokinase (50, 100, or 1000 unit/ml) and incubating for 20 hours at room temperature. After incubation the tubes are centrifuged in a Beckman Microfuge. 25 ul of supernate is added into 1.0 ml volume of 0.03M tris/0.15M NaCl buffer for gamma counting. Counting controls 100 percent lysis are obtained by omitting thrombin (and substituting buffer). The thrombin inhibitors are evaluated for possible interference with fibrinolysis by including the compounds in the overlay solutions at 1, 5, and 10 ug/ml concentrations. Rough approximations of IC50 values are estimated by linear extrapolations from data points to a value which would represent 50 percent of lysis for that particular concentration of fibrinolytic agent.
Anticoaculant Activity
Materials
Dog plasma and rat plasma are obtained from conscious mixed-breed hounds (either sex, hazelton-LRE, Kalamazoo, Mich., U.S.A.) or from anesthetized male Sprague-Dawley rats (Harlan Sprague-Dawley, Inc., Indianapolis, Ind., U.S.A.) by venipuncture into 3.8 percent citrate. Fibrinogen is prepared from in-date ACD human blood as the fraction I-2 according to previous procedures and specifications. Smith, Biochem. J., 185, 1-11 (1980); and Smith, et al., Biochemistry, 11, 2958-2967 (1972). Human fibrinogen is also purchased as 98 percent pure/plasmin free from American Diagnostica, Greenwich, Conn. Coagulation reagents ACTIN, Thromboplastin, and Human plasma are from Baxter Healthcare Corp., Dade Division, Miami, Fla. Bovine thrombin from Parke-Davis (Detroit, Mich.) is used for coagulation assays in plasma.
Methods
Anticoagulation Determinations
Coagulation assay procedures are as previously described. Smith, et al., Thrombosis Research, 50, 163-174 (1988). A CoAScreener coagulation instrument (American LABor, Inc.) is used for all coagulation assay measurements. The thrombin time (TT) is measured by adding 0.05 ml saline and 0.05 ml thrombin (10 NIH units/ml) to 0.05 ml test plasma. The activated partial thromboplastin time (APTT) is measured by incubation of 0.05 ml test plasma with 0.05 ml Actin reagent for 120 seconds followed by 0.05 ml CaCl2 (0.02M). The prothrombin time (PT) is measured by adding 0.05 ml saline and 0.05 ml Thromboplastin-C reagent to 0.05 ml test plasma. The compounds of formula I are added to human or animal plasma over a wide range of concentrations to determine prolongation effects on the TT, APTT and PT assays. Linear extrapolations are performed to estimate the concentrations required to double the clotting time for each assay. Each of the particularly preferred examples of the invention listed above was determined to have a TT value of less than 50 ng/mL. For example, the respective values (in ng/mL) for TT were 6, 6 and 23 for the compounds of Examples 1, 3 and 5.
Animals
Male Sprague Dawley rats (350-425 gm, Harlan Sprague Dawley Inc., Indianapolis, Ind.) are anesthetized with xylazine (20 mg/kg, s.c.) and ketamine (120 mg/kg, s.c.) and maintained on a heated water blanket (37xc2x0 C.). The jugular vein(s) is cannulated to allow for infusions.
Arterio-Venous shunt model
The left jugular vein and right carotid artery are cannulated with 20 cm lengths of polyethylene PE 60 tubing. A 6 cm center section of larger tubing (PE 190) with a cotton thread (5 cm) in the lumen, is friction fitted between the longer sections to complete the arterio-venous shunt circuit. Blood is circulated through the shunt for 15 min before the thread is carefully removed and weighed. The weight of a wet thread is subtracted from the total weight of the thread and thrombus (see J. R. Smith, Br J Pharmacol, 77:29,1982)
FeCl3 model of arterial injury
The carotid arteries are isolated via a midline ventral cervical incision. A thermocouple is placed under each artery and vessel temperature is recorded continuously on a strip chart recorder. A cuff of tubing (0.058 IDxc3x970.077 ODxc3x974 mm, Baxter Med. Grade Silicone), cut longitudinally, is placed around each carotid directly above the thermocouple. FeCl3 hexahydrate is dissolved in water and the concentration (20 percent) is expressed in terms of the actual weight of FeCl3 only. To injure the artery and induce thrombosis, 2.85 ul is pipetted into the cuff to bathe the artery above the thermocouple probe. Arterial occlusion is indicated by a rapid drop in temperature. The time to occlusion is reported in minutes and represents the elapsed time between application of FeCl3 and the rapid drop in vessel temperature (see K. D. Kurz, Thromb. Res., 60:269,1990).
Spontaneous thrombolysis model
In vitro data suggests that peptide thrombin inhibitors inhibit thrombin and at higher concentration may inhibit, other serine proteases, such as plasmin and tissue plasminogen activator. To assess if the compounds inhibit fibrinolysis in vivo, the rate of spontaneous thrombolysis is determined by implanting a labeled whole blood clot into the pulmonary circulation. Rat blood (1 ml) is mixed rapidly with bovine thrombin (4 IU, Parke Davis) and 125I human Fibrogen (5 xcexcCi, ICN), immediately drawn into silastic tubing and incubated at 37xc2x0 C. for 1 hour. The aged thrombus is expelled from the tubing, cut into 1 cm segments, washed 3xc3x97 in normal saline and each segment is counted in a gamma counter. A segment with known counts is aspirated into a catheter that is subsequently implanted into the jugular vein. The catheter tip is advanced to the vicinity of the right atrium and the clot is expelled to float into the pulmonary circulation. One hour after implant, the heart and lungs are harvested and counted separately. Thrombolysis is expressed as a percentage where:       %    ⁢          xe2x80x83        ⁢    Thrombolysis    =                    (                              injected            ⁢                          xe2x80x83                        ⁢            cpm                    -                      lung            ⁢                          xe2x80x83                        ⁢            cpm                          )                    injected        ⁢                  xe2x80x83                ⁢        cpm              xc3x97    100  
The fibrinolytic dissolution of the implanted clot occurs time-dependently (see J. P. Clozel, Cardiovas. Pharmacol., 12:520, 1988).
Coagulation parameters
Plasma thrombin time (TT) and activated partial thromboplastin time (APTT) are measured with a fibrometer. Blood is sampled from a jugular catheter and collected in syringe containing sodium citrate (3.8 percent, 1 part to 9 parts blood). To measure TT, rat plasma (0.1 ml) is mixed with saline (0.1 ml) and bovine thrombin (0.1 ml, 30 U/ml in TRIS buffer; Parke Davis) at 37xc2x0 C. For APTT, plasma (0.1 ml) and APTT solution (0.1 ml, Organon Teknika) are incubated for 5 minutes (37xc2x0 C.) and CaCl2 (0.1 ml, 0.025M) is added to start coagulation. Assays are done in duplicate and averaged.
Index of Bioavailability
A measure of bioactivity, plasma thrombin time (TT), serves as a substitute for the assay of parent compound on the assumption that increments in TT resulted from thrombin inhibition by parent only. The time course of the effect of the thrombin inhibitor upon TT is determined after i.v bolus administration to anesthetized rats and after oral treatment of fasted conscious rats. Due to limitations of blood volume and the number of points required to determine the time course from time of treatment to the time when the response returns to pretreatment values, two populations of rats are used. Each sample population represents alternating sequential time points. The average TT over the time course is used to calculate area under the curve (AUC). The index of bioavailability is calculated by the formula shown below and is expressed as percent relative activity.
The area under the curve (AUC) of the plasma TT time course is determined and adjusted for the dose. This index of bioavailability is termed xe2x80x9c% Relative Activityxe2x80x9d and is calculated as       %    ⁢          xe2x80x83        ⁢    Relative    ⁢          xe2x80x83        ⁢    Activity    =                    AUC        ⁢                  xe2x80x83                ⁢        po                    AUC        ⁢                  xe2x80x83                ⁢        iv              xc3x97                  Dose        ⁢                  xe2x80x83                ⁢        iv                    Dose        ⁢                  xe2x80x83                ⁢        po              xc3x97    100  
Compounds
Compound solutions are prepared fresh daily in normal saline and are injected as a bolus or are infused starting 15 minutes before and continuing throughout the experimental perturbation which is 15 minutes in the arteriovenous shunt model and 60 minutes in the FeCl3 model of arterial injury and in the spontaneous thrombolysis model. Bolus injection volume is 1 ml/kg for i.v., and 5 ml/kg for p.o. and infusion volume is 3 ml/hr.
Statistics
Results are expressed as means xc2x1SEM. One-way analysis of variance is used to detect statistically significant differences and then Dunnett""s test is applied to determine which means are different. Significance level for rejection of the null hypothesis of equal means is P less than 0.05.
Animals
Male dogs (Beagles; 18 months -2 years; 12-13 kg, Marshall Farms, North Rose, N.Y. 14516) are fasted overnight and fed Purina certified Prescription Diet (Purina Mills, St. Louis, Mo.) 240 minutes after dosing. Water is available ad libitum. The room temperature is maintained between 66-74xc2x0 F.; 45-50 percent relative humidity; and lighted from 0600-1800 hours.
Pharmacokinetic model
Test compound is formulated immediately prior to dosing by dissolving in sterile 0.9 percent saline to a 5 mg/ml preparation. Dogs are given a single 2 mg/kg dose of test compound by oral gavage. Blood samples (4.5 ml) are taken from the cephalic vein at 0.25, 0.5, 0.75, 1,2,3,4 and 6 hours after dosing. Samples are collected in citrated Vacutainer tubes and kept on ice prior to reduction to plasma by centrifugation. Plasma samples are analyzed by HPLC-MS. Plasma concentration of test compound is recorded and used to calculate the pharmacokinetic parameters: elimination rate constant, Ke; total clearance, Clt; volume of distribution, VD; time of maximum plasma test compound concentration, Tmax; maximum concentration of test compound of Tmax, Cmax; plasma half-life, t0.5; and area under the curve, A.U.C.; fraction of test compound absorbed, F.
Canine Model of Coronary Artery Thrombosis
Surgical preparation and instrumentation of the dogs are as described in Jackson, et al., Circulation, 82, 930-940 (1990). Mixed-breed hounds (aged 6-7 months, either sex, Hazelton-LRE, Kalamazoo, Mich., U.S.A.) are anesthetized with sodium pentobarbital (30 mg/kg intravenously, i.v.), intubated, and ventilated with room air. Tidal volume and respiratory rates are adjusted to maintain blood PO2, PCO2, and pH within normal limits. Subdermal needle electrodes are inserted for the recording of a lead II ECG.
The left jugular vein and common carotid artery are isolated through a left mediolateral neck incision. Arterial blood pressure (ABP) is measured continuously with a precalibrated Millar transducer (model (MPC-500, Millar Instruments, Houston, Tex., U.S.A.) inserted into the carotid artery. The jugular vein is cannulated for blood sampling during the experiment. In addition, the femoral veins of both hindlegs are cannulated for administration of test compound.
A left thoracotomy is performed at the fifth intercostal space, and the heart is suspended in a pericardial cradle. A 1- to 2-cm segment of the left circumflex coronary artery (LCX) is isolated proximal to the first major diagonal ventricular branch. A 26-gauge needle-tipped wire anodal electrode (Teflon-coated, 30-gauge silverplated copper wire) 3-4 mm long is inserted into the LCX and placed in contact with the intimal surface of the artery (confirmed at the end of the experiment). The stimulating circuit is completed by placing the cathode in a subcutaneous (s.c.) site. An adjustable plastic occluder is placed around the LCX, over the region of the electrode. A precalibrated electromagnetic flow probe (Carolina Medical Electronics, King, N.C., U.S.A.) is placed around the LCX proximal to the anode for measurement of coronary blood flow (CBF). The occluder is adjusted to produce a 40-50 percent inhibition of the hyperemic blood flow response observed after 10-s mechanical occlusion of the LCX. All hemodynamic and ECG measurements are recorded and analyzed with a data acquisition system (model M3000, Modular Instruments, Malvern, Pa. U.S.A.).
Thrombus Formation and Compound Administration Regimens
Electrolytic injury of the intima of the LCX is produced by applying 100-xcexcA direct current (DC) to the anode. The current is maintained for 60 min and then discontinued whether the vessel has occluded or not. Thrombus formation proceeds spontaneously until the LCX is totally occluded (determined as zero CBF and an increase in the S-T segment). Compound administration is started after the occluding thrombus is allowed to age for 1 hour. A 2-hour infusion of the compounds of the present invention at doses of 0.5 and 1 mg/kg/hour is begun simultaneously with an infusion of thrombolytic agent (e.g. tissue plasminogen activator, streptokinase, APSAC). Reperfusion is followed for 3 hour after administration of test compound. Reocclusion of coronary arteries after successful thrombolysis is defined as zero CBF which persisted for xe2x89xa730 minutes.
Hematology and template bleeding time determinations
Whole blood cell counts, hemoglobin, and hematocrit values are determined on a 40-xcexcl sample of citrated (3.8 percent) blood (1 part citrate: 9 parts blood) with a hematology analyzer (Cell-Dyn 900, Sequoia-Turner. Mount View, Calif., U.S.A.). Gingival template bleeding times are determined with a Simplate II bleeding time device (Organon Teknika Durham, N.C., U.S.A.). The device is used to make 2 horizontal incisions in the gingiva of either the upper or lower left jaw of the dog. Each incision is 3 mm widexc3x972 mm deep. The incisions are made, and a stopwatch is used to determine how long bleeding occurs. A cotton swab is used to soak up the blood as it oozes from the incision. Template bleeding time is the time from incision to stoppage of bleeding. Bleeding times are taken just before administration of test compound (0 min), 60 min into infusion, at conclusion of administration of the test compound (120 min), and at the end of the experiment.
All data are analyzed by one-way analysis of variance (ANOVA) followed by Student-Neuman-Kuels post hoc t test to determine the level of significance. Repeated-measures ANOVA are used to determine significant differences between time points during the experiments. Values are determined to be statistically different at least at the level of p less than 0.05. All values are mean xc2x1SEM. All studies are conducted in accordance with the guiding principles of the American Physiological Society. Further details regarding the procedures are described in Jackson, et al., J. Cardiovasc. Pharmacol., 21, 587-599 (1993).
Compared to the corresponding amidino-phenyl compounds, the compounds of the instant invention, in which a hydroxy group is juxtaposed ortho to the amidino group, possess physio-chemical properties which are much more favorable for oral absorption. The logD (D=octanol/water distribution coefficient) at pH 7.4 [logD(7.4)] observed for the compound of Example 5 [logD(7.4)=1.91] exhibits a more favorable value than that of the reference compound [logD(7.4)=xe2x88x923.89], a change [xcex94logD(7.4)] of 5.80 log units. For the compound of Example 3 [logD(7.4)=0.55], compared with the corresponding amidino phenyl compound, xcex94logD(7.4)=1.13 log units was observed.
The following Examples are provided to further describe the invention and are not to be construed as limitations thereof.
The abbreviations used in the examples have the following meanings.
Amino acids: Azt=azetidine-2-carboxylic acid, Phe=phenylalamine, hPro=homo-proline, Pro=proline, Cha=xcex2=cyclohexylalanine, Ohi=[2S-(2xcex1,3axcex2,7axcex2)]-octahydro-indol-2-carboxylic acid, (1R,4aR,8aR)-1-Piq=(1R,4aR,8aR)-1-perhydro-isoquinolinecarboxylate, Sar=sarcosine (N-methyl-glycine).
Anal.=elemental analysis
Boc=t-butyloxycarbonyl
Bn=benzyl
BOP-Cl=bis(2-oxo-3-oxazolidinyl)phosphinic chloride
t-Bu=t-butyl
n-BuLi=butyllithium
Cbz=benzyloxycarbonyl
18-Crown-6=1,4,7,10,13,16-hexaoxacyclooctadecane
DIBAL=diisobutylaluminum hydride
DMF=dimethylformamide
DMSO=dimethylsulfoxide
Et=ethyl
EtOAc=ethyl acetate
Et2O=diethyl ether
EtOH=ethanol
FAB-MS=fast atom bombardment mass spectrum
FD-MS=field desorption mass spectrum
HPLC=High Performance Liquid Chromatography
HRMS=high resolution mass spectrum
HOBT=1-hydroxybenzotriazole hydrate
i-PrOH=isopropanol
IR=Infrared Spectrum
Me=methyl
MeOH=methanol
NMR=Nuclear Magnetic Resonance
RPHPLC=Reversed Phase High Performance Liquid Chromatography
SiO2 silica gel
TEA=triethylamine
TFA=trifluoroacetic acid
THF=tetrahydrofuran
TLC=thin layer chromatography
Ts=tosyl (p-toluenesulfonyl)
The following parameters for preparative RPHPLC were employed: Solvent A: 0.05% aqueous hydrochloric acid (1.5 mL concentrated hydrochloric acid in 3 L water); Solvent B: acetonitrile; Gradient: as defined in each Example; Column: Vydac C18xe2x88x925 cmxc3x9725 cm; Flow rate: 10 mL/minute.
Unless otherwise stated, pH adjustments and work up are with aqueous acid or base solutions. 1H-NMR indicates a satisfactory NMR spectrum was obtained for the compound described. IR indicates a satisfactory infra red spectrum was obtained for the compound described.